Triacylglycerol

hannah kemp, Catherine Paul
  • Author
    hannah kemp

    Hannah is a graduate of DePaul University in Chicago, IL with a BS in Biological Sciences and a minor in Journalism. Since her graduation in 2017, she has been involved in various ecological research projects in Michigan, Wisconsin, Minnesota, Alaska, and Massachusetts. Her areas of interest include marine biology, ecology, genetics, and environmental science. Hannah has also worked for four years as a science tutor and interned at Chicago's Field Museum of Natural History in 2018.

  • Instructor
    Catherine Paul

    Catherine has taught high school science and has a master's degree in biology.

Learn about triacylglycerol. Understand what triacylglycerol is, its structure, and its function, and discover that its other name is triglyceride. Updated: 05/27/2022

What Is Triacylglycerol?

It is well known that eating high amounts of ''unhealthy'' fats can have negative impacts on the body. Lots of butter, dairy, and fatty meats can lead to heart disease, hardening of the arteries, obesity, stroke, and even death. But what are unhealthy fats? What are healthy fats? And how does the body use and store them?

Triacylglycerol, more commonly known as triglycerides, are a fat (lipid) found in the blood. Triglycerides are esters, composed of a glycerol molecule and three fatty acids. These esters are produced by the liver and used in the long-term storage of energy. After eating, they store calories that are not immediately used by the body. Calories are converted into triglycerides by the liver. Some triglycerides remain in the liver and others are sent via the bloodstream for storage in the adipose tissue. Hormones trigger the release of triglycerides for energy in between meals. It is important to monitor triglyceride levels. Eating more calories than you burn, especially from high-carbohydrate foods, can result in serious health issues.

Energy Reserves and Functions

Let's start with a riddle: Name one thing many of us have and want to lose? The answer: fat!

Fat commonly gets a bad rap when it comes to our health. But the truth is, our bodies are designed to have a fat reserve of around 21% for men and 26% for women. When our bodies undergo long periods of food shortages, the fats found in triacylglycerol, a combination of fatty acids and the chemical compound glycerol, serve as an energy resource. For example, your body has a day's worth if sugar reserves, but once is has used that up your body will turn to your adipose tissue, a connective tissue that sores fat, to survive.

But why do we need fat for energy? Why can't we just store sugar?

Fat is special in that it can produce six times the energy of the same amount of common sugar. When our body gets the signal that our blood sugar supply is low, fat is released into the bloodstream.

Fats are also very easy to store because they are non-polar and water insoluble, which means they cannot be dissolved in water. As a result, we don't need to combine our fats with water in order to store them. For example, a piece of butter dropped into a glass of water would remain intact, while a spoonful of sugar would dissolve in water. Animals have special cells called adipocytes, which both create fat and store it in fat globules within the cell.

Adipose tissue, found mostly just under our skin, functions not only as energy reserves, but also as thermal insulation, to keep our bodies warm in lower temperatures. Warm-blooded water animals, such as whales, seals and penguins, need a substantial fat layer to keep them warm in cold climates.

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Triglyceride Structure

Triglycerides are esters, made up of a glycerol molecule bound to three fatty acid molecules. Glycerol is a simple sugar alcohol with three available hydroxyl functional groups. Fatty acids are long carbon chains, typically containing between 12 and 24 carbons, bound to a carboxyl group. Esterification between the hydroxyl and carboxyl groups of the glycerol and fatty acid results in a triglyceride. The polar nature of hydroxyl and carboxyl groups results in triglycerides nonpolar, hydrophobic, and insoluble in water. Because lipids are insoluble they are not easily broken down by the body, making them easy to store.

Saturated Triglycerides

Some triglycerides are classified as saturated. Saturated triglycerides are composed of a single glycerol bound to three fatty acid chains. In a saturated triglyceride, the carbon chains are composed of only single bonds. They are, therefore ''saturated'' with as many hydrogen molecules as possible. Saturated fats are commonly found in butter, cheese, lard, and meat and are less healthy than unsaturated fats.


An unsaturated triglyceride, containing all single hydrogen bonds in its carbon chain

A diagram of an unsaturated triglyceride, containing all single hydrogen bonds


Unsaturated Triglycerides

Triglycerides can also be unsaturated. Unsaturated triglycerides are also composed of a single glycerol and three fatty acid chains. However, an unsaturated triglyceride contains at least one double bond in its carbon chain. This prevents additional hydrogens from bonding, making the molecule ''unsaturated'' with hydrogen. Unsaturated fats are considered to be healthy fats and are commonly found in nuts, avocados, and seed oils.


An unsaturated triglyceride molecule, containing multiple double bonds in its carbon chains

A diagram of an unsaturated triglyceride molecule, containing double bonds

Triglycerides Function

When an individual eats a meal, they are consuming calories in the form of carbohydrates, proteins, and fat. Typically, an adult human requires around 2,000 calories per day. If an individual consumes more calories than their body needs, those calories are converted into triglycerides by the liver. Triglycerides act as energy reserves for long-term storage and can be stored in both the liver and in the body's adipose, or fat, tissue. From the liver, they are released into the bloodstream for use by the body or for storage in the adipose tissue. When the body needs energy in between meals, hormones signal the fat cells to release triglycerides into the blood. Energy is stored within the long carbon tails of the fatty acids and is released when the fatty acid tails are broken down.

Structure

We get our dietary fat from plants, fish and animals, mostly in the form of triacylglycerols, or triglycerides, typically made by the pancreas. Let's break that big word down. We'll start with the prefix, 'tri', which refers to the three fatty acids. At the end of the word, we have glycerol, a sugar alcohol composed of one glycerol unit.

Triglyceride structure
Triglyceride Structure

You may have heard the terms 'saturated' and 'unsaturated' fat in reference to food sources. Triacylglycerols can vary in the length of their fatty acid chains and the saturation level of those chains. Saturation refers to the extent of the hydrogen (H) bonds: to say that a fat is 'saturated' means that it has all the hydrogen bonds possible.

Butter Contains Saturated Fat
Butter Contains Saturated Fat

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Video Transcript

Energy Reserves and Functions

Let's start with a riddle: Name one thing many of us have and want to lose? The answer: fat!

Fat commonly gets a bad rap when it comes to our health. But the truth is, our bodies are designed to have a fat reserve of around 21% for men and 26% for women. When our bodies undergo long periods of food shortages, the fats found in triacylglycerol, a combination of fatty acids and the chemical compound glycerol, serve as an energy resource. For example, your body has a day's worth if sugar reserves, but once is has used that up your body will turn to your adipose tissue, a connective tissue that sores fat, to survive.

But why do we need fat for energy? Why can't we just store sugar?

Fat is special in that it can produce six times the energy of the same amount of common sugar. When our body gets the signal that our blood sugar supply is low, fat is released into the bloodstream.

Fats are also very easy to store because they are non-polar and water insoluble, which means they cannot be dissolved in water. As a result, we don't need to combine our fats with water in order to store them. For example, a piece of butter dropped into a glass of water would remain intact, while a spoonful of sugar would dissolve in water. Animals have special cells called adipocytes, which both create fat and store it in fat globules within the cell.

Adipose tissue, found mostly just under our skin, functions not only as energy reserves, but also as thermal insulation, to keep our bodies warm in lower temperatures. Warm-blooded water animals, such as whales, seals and penguins, need a substantial fat layer to keep them warm in cold climates.

Structure

We get our dietary fat from plants, fish and animals, mostly in the form of triacylglycerols, or triglycerides, typically made by the pancreas. Let's break that big word down. We'll start with the prefix, 'tri', which refers to the three fatty acids. At the end of the word, we have glycerol, a sugar alcohol composed of one glycerol unit.

Triglyceride structure
Triglyceride Structure

You may have heard the terms 'saturated' and 'unsaturated' fat in reference to food sources. Triacylglycerols can vary in the length of their fatty acid chains and the saturation level of those chains. Saturation refers to the extent of the hydrogen (H) bonds: to say that a fat is 'saturated' means that it has all the hydrogen bonds possible.

Butter Contains Saturated Fat
Butter Contains Saturated Fat

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Frequently Asked Questions

What are examples of triacylglycerol?

Triacylglycerols are fats. These fats can be saturated or unsaturated. Unsaturated fats are the healthy fats and are found in foods such as nuts, seeds, avocado, and fish oil. Saturated fats are the unhealthy fats and are found in foods such as butter, lard, and fatty meat.

What is the function of triacylglycerol?

Triacylglycerols, or triglycerides, store energy for the body. Calories are stored in the form of triglycerides in the liver and adipose tissue of the body. Between meals, when the body needs energy, hormones trigger the release of triglycerides into the blood stream.

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